1. Field of the Invention
This invention relates to systems and methods for modulating and scanning multi-chrominant light beams, particularly laser beams, to provide a single color-modulated information carring beam of high intensity using a single modulator.
2. Description of the Prior Art
Virtually from the first showing of the practical workability of the laser principle, investigators have considered the use of this coherent, concentrated high intensity light source as a means of carrying information and generating visual displays, particularly color television pictures. The use of laser beams has significant potential advantages, particularly for extremely large displays, such as are now provided almost solely by the Eidophor process or by photographic projection techniques.
The generation of a color picture utilizing laser beams has heretofore usually been based upon the employment of three separate beams corresponding to the different primary colors, three separate modulators, an optical and scanning system for combining the beams at a single axis or three closely adjacent axes, and a combined beam projected over a considerable distance onto a viewing screen. The operative drawbacks of such systems, derived principally from their plural beam aspect, have essentially precluded general adoption of laser-based visual displays. For example, multiple and complex optical elements and arrangements are difficult to align and maintain in alignment as well as being costly and cumbersome. The initial costs, and power losses attendant upon, the usage of separate lasers and modulators have generally been prohibitive.
Although acousto-optical modulators are commercially available that successfully amplitude modulate the intensity of a beam of a given wavelength, a number of problems must be overcome in order to modulate more than one wavelength and obtain high optical efficiency with such an element. The interaction within the modulator between the acoustic wave and the light beam is complex, and a number of factors militate against maximum light output transmission. Each modulating signal acts differently upon each incident wavelength, introducing different beam deflections as well as modulation. Further, video signals are wideband signals and it is well known that certain relatively minor signal distortions can introduce unacceptable picture degradation. Moreover, a large TV display requires maximum utilization of the energy in the transmitted beam, inasmuch as illumination from the beam must be distributed over a wide area. Viewed in another way, the laser is a relatively inefficient generator of light and any modulation and scanning system that could generate a comparable amount of display light utilizing a smaller laser power source would be inherently advantageous.
Therefore, there has been a recognized but unfulfilled need for a visual display system utilizing laser-generated light which permits multi-wavelength signals to be carried by and modulated in a single laser beam.